Online reference needing number and name (7)
I believe the answer is:
hashtag
'online reference' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.
'number and name' is the wordplay.
'number' becomes 'hash' (I can't justify this - if you can you should give a lot more credence to this answer).
'and' says to put letters next to each other.
'name' becomes 'tag' (tag can mean a name or label).
'hash'+'tag'='HASHTAG'
'needing' is the link.
Can you help me to learn more?
(Other definitions for hashtag that I've seen before include "Octothorp" , "Social media identifier" , "Label on a message on Twitter" , "Label on a Twitter post" , "Symbol used to indicate the subject of a Twitter message" .)